1. Field
This description relates in general to automated data storage libraries, and more particularly, to inventory management of data storage media in an automated data storage libraries.
2. Description of Related Art
Automated data storage libraries are known for providing cost effective storage and retrieval of large quantities of data. The data in automated data storage libraries is typically stored on media of data storage cartridges that are, in turn, stored in storage slots, often referred to as cells, inside the library in a fashion that renders the media, and its resident data, accessible for physical retrieval. Such data storage cartridges are commonly termed “removable media.”
In an effort to increase storage capacity, deep slot technology allows for storage cells that contain more than a single data storage cartridge. Such storage libraries allow for higher density, or more cartridges stored per square foot. In ‘deep slot’ libraries, two or more cartridges may be stored in a multi-cartridge deep slot cell, arrayed in series, one behind the other, in tiers ranging from a front-most tier to a rearmost tier.
In automated tape libraries one function of the library is to manage the physical location of cartridges within the library. A process of determining the physical locations of all the cartridges in the library is often referred to as an “inventory.” In many automated tape libraries, an inventory is performed by a robotic accessor scanning the serial number label on the front of each tape cartridge in the library as well as all locations in the library to determine which slots are empty and which are full.
In automated tape libraries where a three dimensional (3D) storage array is used to efficiently store a large number of cartridges, scanning the front label on the cartridge can be a time consuming task as the robotic accessor typically moves each tape cartridge located in front of a deeper tape cartridge stored inside the deep slot in order to scan the serial number label on the next-in-line tape cartridge. In very large automated tape libraries, with thousands of tape cartridges, the inventory process can take several hours to complete. Inventories are often initiated upon initial automated tape library installation, or when a bulk load/unload of tape cartridges occurs, or when a customer is required to verify a physical inventory.
One known method for an automated tape library inventory with deep slots involves the robotic accessor moving tape cartridges within the library to create two empty deep slots at the top or bottom of a column of deep slots within the automated tape library. Then moving cartridges with multiple grippers, each cartridge is moved from the full cells below or above the empty cells, scanning each cartridge as it goes. Once all the cartridges are moved from the original location to an original empty cell, the original location cells now become empty and the next two cells can follow the same process. The process is repeated for each column of the array of slots. In this manner, the empty cells are moved throughout the automated tape library as each tape cartridge is moved up or down two cells from its original location.